Thanks for the report, I’ll look into this.
A common issue with large keys are the long transfer times. If the connection is wonky in the slightest, GPG instantly trips.
I recommend not using RSA, ans switching to elliptic curves instead. See e.g. https://cheapsslsecurity.com/p/ecc-vs-rsa-comparing-ssl-tls-algorithms/ for a comparison on key size.